The present invention relates generally to the control of dynamoelectric machines and more particularly to a generator system of the type employing a self-excited field winding to which power may be selectively applied to achieve stable and accurate control of the generator output.
It is a common objective in the art to provide a generator system which includes means for insuring startup of the generator from a zero condition to a rated condition using only the residual magnetism of the field and to use the same control system on a wide variety of generators. One such known system employs a self-excited generator field winding which receives excitation power from the generator output and which field winding may be selectively short-circuited for a variable period of time during each cycle of normal generator operation such that the time period of short-circuiting of the field winding controls the excitation and hence the generator operation. An example of such a system may be found in U.S. Pat. No. 3,369,171, "Control Circuits", by Lawrence J. Lane, issued Feb. 13, 1968, and assigned to the assignee of the present invention. Control circuits such as that described in the aforementioned patent, and modifications thereof, employ a feedback path which is responsive to an operating parameter; e.g., the voltage of a bridge circuit which supplies power to the field, to develop a control signal utilized to vary the time during which the field winding is short-circuited. While these systems operate satisfactorily for the most part and are a vast improvement in economy and performance over still older systems employing an entirely separate and distinct means for supply excitation to the field winding, it is quite often the case that the feedback is nonlinear such that the overall control of the generator system is not as accurate as is desirable in some instances.